Heat exchange through the muskrat tail. Evidence for vasodilator nerves to the skin.

Abstract

AbstractThe importance of peripheral vascular adjustments in the regulation of thermal balance has been studied in 25 adult muskrats. This animal has a pelage of high insulative value while the tail is naked. The importance of the naked tail for maintenance of thermal balance was studied by plethysmographic techniques and measurements of tail and rectal temperatures. When subjecting the animal to a positive heat load by general body heating or following excercise, the tail skin temperatures rose to 35–37° C. Tail blood flow increased concomitantly by a factor of more than 400. The vasodilatation and subsequent increase in tail blood flow prevented heat accumulation and increase in rectal temperature during the positive heat load. Nerve block of the tail before heating or excercise precluded the described increase in tail blood flow and hyperthermia resulted. Nerve block at maximum blood flow led to a prompt decrease in tail temperature and a rapid increase in rectal temperature. It is concluded that the muskrat tail is an indispensible heat exchanger, reducing excess heat from increased metabolism or general body heating. The data indicate that the conspicious changes in tail blood flow are mediated through a sympathetic vasodilator mechanism.